On occasion, I go for a run with one of my mates, who I also ride with. I would guess he weighs about 60-70% of what I do. On a bike, I'm easily as fast as he is, probably a bit faster on the downs and little slower up the hills 😆

Now, when we go running, I've got no chance of keeping up – I end up breathing through my hoop pretty sharpish. Is it a case of me needing to do more running, or is it just a fact of life that I'm not going to run like he can until I lose some weight? I would think our fitness aerobically must be pretty similar if I can keep up with him on the bike.

I am chunkier than most my mates and am quicker purely as I do it more often.

More running sonny jim.

Have similar with a mate – he's about 15 stone, I'm just over 11. He's very rapid on a bike but I completely slay him running.

I think you can "get away" with a bit more weight on a bike – he's a bit porky despite being fit but very strong with lots of cardio fitness. When running any excess weight hinders you – very rare to see very bulky good runners.

You're lifting your entire body weight with every step. That adds up.

And he climbs faster than you on a bike so has a better power:weight ratio.

Genetics?

His leg springs [or whatever] are more suited to running than yours are?

I remember when I first started running a couple of years back. I could do 40-50 miles XC on the bike, but after several hundred yards running I was dying 😐